This invention applies to the general use of self-propelled vehicles to perform manufacturing, inspection, maintenance or service tasks on structures. This invention further considers these self-propelled vehicles operating in a climbing configuration; that is traversing on inclined, vertical or overhead surfaces such that gravity does not provide the necessary forces directed toward the climbing surface to maintain equilibrium on a desired path. Examples would be climbing a vertical wall or climbing overhead or any other situation in which additional forces (beyond those directed outward from the surface are desired or required to maintain or improve vehicle performance. Finally, this invention applies to the situation in which suction or pressure differential acting against atmospheric pressure provides a majority of this additional force. An example of such an environment to which the present invention is contemplated is performing manufacturing operations on interior or exterior portions of ships. Other environments could include but are not limited to civil structures, wind mills, aircraft, tanks, pipes, structural members and toys.
A variety of climbing vehicles have been proposed to operate in climbing configurations that make use of suction to provide a stabilizing forces. In a general sense, these vehicles could be grouped into three categories; discrete suction devices located on members moving relative to the chassis, one or a smaller number of suction devices created as a chamber generally attached to the vehicle chassis.
In the first category, a number of discrete suction creating elements that are fixed to portions of the vehicle that are moving relative to the chassis. These generally fall into three sub-categories: i) legged devices with one suction device located at the distal end of each leg as shown for example in DE19907437A1, U.S. Pat. Nos. 6,105,695A, 5,121,805A, where the legs can move independently, examples demonstrate four to six legs commonly, ii) bar-type devices with several suction devices located on a bar or track that is moved relative to the chassis, as shown for example in CN2475891Y, U.S. Pat. No. 4,674,949A, WO1983002419A1, WO2013048263A1, which commonly employ two or more translating bars and in some cases a rotating plate, and iii) endless-track devices with suction elements located on an endless track moving relative to the vehicle chassis. This approach has the advantage of keeping the suction element stationary to the climbing surface during a period in which force is applied, allowing better sealing options and can be used to minimize the energy required to create and maintain a suction. The disadvantage is associated with often a more complex propulsion system and the need to attach and create initial suction at the suction devices.
In the second category, one or a small number of suction devices are created in a chamber that in generally attached to and moves with the vehicle chassis as shown for example in U.S. Pat. Nos. 7,775,312B2, 4,926,957A, 5,536,199 and 5,752,577A, 4,926,957, 5,536,199, 5,752,577, 6,102,145, 3,268,023. Several variations to this approach are suggested. This approach has the advantage of allowing for a more simple propulsion system. The disadvantage lies in the requirement to maintain a certain level of seal to minimize the passage of air into the suction chamber. On smooth surfaces, a simple seal is used, with several methods shown to allow a more flexible seal for surfaces with surface variations including inflated and variable geometries in the seal (U.S. Pat. No. 3,268,023). A novel method is demonstrated in U.S. Pat. No. 7,775,312B2 that employs a combination of endless track and rollers to create a seal that provides limited relative motion with respect to the surface and moves the moving seal portions into the vehicle. This device also allows for more variable geometry protruding from the climbing surface through deformation of the seals. While these methods demonstrate the ability to create a suction chamber with a degree of sealed perimeter on flat and not-smooth surfaces, these inventions to not permit significant variations in the surface geometry including the ability to transition over corners in a convex or concave fashion. This capability is a desirable feature and can significantly improve the ability of this type of mobile robotic vehicle.